Concentrated or dilutable solutions or dispersions, preparation method and uses

ABSTRACT

A heat exchanger for heat extraction of a refrigerating fluid such as CO2, comprising at least one collecting box defined by a solid body ( 41 ) with a thick wall capable of resisting the high pressure of said fluid, and communicating with a row of flat tubes ( 44 ). In order to limit bulkiness in the width of the heat exchanger, only one part of the length of the cross section of the tubes is located opposite the inner volume of said body, whereby tightness of the fluidic communication between the tubes and the inner volume is obtained by means of a cradle ( 50 ) in the form of a shaped strip receiving the body and brazed thereto on the periphery of the tubes. The heat exchanger can be used to air condition passenger compartments in vehicles.

The invention relates to a heat exchanger comprising at least onemanifold the internal volume of which is defined by at least onelongitudinal bore formed in an elongate solid body, and is in fluidcommunication with a row of tubes which are mutually aligned in theaxial direction of the bore or bores, elongate parallel to one anotherin a first direction substantially perpendicular to the said axialdirection and having an elongate cross section in a second directionsubstantially perpendicular to the axial direction and substantiallyperpendicular to the said first direction.

Such heat exchangers are used especially for extracting heat from arefrigerant fluid in a motorvehicle air-conditioning installation, and,more particularly, when the refrigerant fluid is one of those which,like CO₂, have to be subject to very high pressures, for example ofseveral hundred bar. The manifolds used in the conventionalair-conditioning condensers, comprising a tubular wall formed from oneor more rolled metal sheets, would not in fact withstand such pressures,and a solid component is required in order to furnish sufficient wallthickness.

However, if the ends of the tubes open out directly into a bore definingthe internal volume of the manifold, as they do within the tubular,sheet-metal wall of conventional manifolds, the high wall-thickness ofthe manifold adds to the space taken up by the tubes in the seconddirection, correspondingly increasing the overall space required for theheat exchanger.

The object of the invention is to remedy this drawback, and to reducethe overall size of the heat exchanger in the second direction, for agiven length of the cross section of the tubes.

The invention especially envisages a heat exchanger of the kind definedin the introduction, and provides for only a part of the length of thecross section of the tubes to project, along the said first direction,into the said internal volume, the leaktightness of the fluidcommunication between the tubes and the internal volume being obtainedby means of a cradle in the form of a profiled strip, accommodating thesaid body and brazed to it and to the periphery of the tubes.

Optional characteristics of the invention, which are complementary oralternative, are set out below:

at least one end of the length of the cross section of the tubesprojects along the said first direction beyond the bore or the set ofbores in the second direction;

an intermediate part of the length of the cross section of the tubesprojects along the said first direction between two bores defining thesaid internal volume;

one end of each tube is engaged in a slot formed in the said body,elongate in the second direction, opening out at its two ends and thebottom of which is interrupted by the said internal volume, the saidcradle being applied to the body in such a way as to cover over the saidslots and exhibiting, opposite them, elongate apertures for theleaktight passage of the tubes;

each slot features two lateral regions of a reduced depth the bottom ofwhich serves as an abutment for the end of the tube and a deeper centralregion defining a free space which communicates with the inside of thetube;

one end of each tube is engaged so as to be leaktight to the fluid in astamped cup of the cradle, the bottom of which is itself housed in aleaktight way in a transverse notch of the body and traversed by atleast one aperture for fluid communication between the tube and the saidinternal volume;

the body and the cradle feature means for mutual mechanical fastening;

the said fastening means comprise two step features extending in theaxial direction on the outer surface of the body, respectively on eitherside of a plane passing through the axes of the tubes, and interactingwith teeth of the cradle;

each tooth is formed at the free end of a lug extending substantially ina radial plane, each lug being interposed in the axial direction betweentwo cups;

the manifold includes at least one transverse partition delimiting, inthe axial direction, at least one chamber which forms part of the saidinternal volume, engaged in an aperture of the body which is coveredover by the cradle;

the manifold includes at least one transverse partition delimiting, inthe axial direction, at least one chamber which forms part of the saidinternal volume, engaged in an aperture of the body beyond which itprotrudes and carrying means for mechanical fastening onto the peripheryof the body.

The characteristics and advantages of the invention will be set out inmore detail in the description below, by referring to the attacheddrawings.

FIG. 1 is a partial view in exploded perspective of a heat exchangerintended for extracting heat from CO₂ in the supercritical state at highpressure, used as a refrigerant fluid in a motor-vehicleair-conditioning circuit.

FIGS. 2 and 3 are views in cross section and in axial sectionrespectively of the part of the heat exchanger represented in FIG. 1.

FIGS. 4 and 5 are partial views in perspective of two other heatexchangers according to the invention.

FIG. 6 is a partial end view of the exchanger of FIG. 5.

FIGS. 7 and 8 are partial views in longitudinal section and from theside of this same exchanger.

The heat exchanger represented in FIGS. 1 to 3 comprises a manifoldformed essentially by a solid metal body 1 having the general externalshape of an elongate axisymmetric cylinder. The body 1 is pierced by anaxial through-bore 2 which confers on it the form of a thick-walledtube. The body 1 is produced by extrusion, for example.

Transverse slots 3, regularly spaced from one another in the axialdirection, are formed in the body 1. Each slot 3 is horizontallyelongate, as seen in FIG. 2, and opens out outside the body at its twoends as well as downwards over its entire length. Its bottom isinterrupted, furthermore, by the bore 2 which is thus in fluidcommunication with the slot. Each slot serves to accommodate the upperend of a vertically elongate tube 4, as seen in the figures, andfeaturing two main faces situated in respective planes perpendicular tothe longitudinal axis A of the body 1 and of the bore 2, conferring onit an elongate cross section from left to right in FIG. 2. Each tube 4is pierced by a multiplicity of longitudinal channels mutually alignedalong its width (that is to say along the length of its cross section),these channels defining separate paths for the circulation of the fluid.The tubes 4 are mutually aligned in the direction of the axis A,alternating with spacers 6 each consisting of a corrugated strip, thecorrugation crests of a spacer coming into contact alternately with thetwo tubes which frame it.

According to the invention, the width of the tubes is greater than thediameter of the bore 2, in such a way that only the channels 5 situatedin a central region of this width open out directly into the bore 2,while the other channels open out opposite the thick wall of the body 1,on either side of the bore, as is seen clearly in FIG. 2. This resultsin a reduction in the overall size of the manifold, and consequently ofthe heat exchanger as a whole, in the direction of the width of thetubes, for a given value thereof. In order to allow both precisepositioning of the tubes and effective fluid communication between themarginal channels and the bore 2, the bottom of the slots is situated attwo different levels. On each of the longitudinal sides of a slot, thebottom 7 thereof is at a lower level and forms an abutment for thelateral edges of the end of the tube 4. In the central region of thewidth of the slot, its bottom 8 is at a higher level, consequentlyspaced away from the end of the tube, so as to define two horizontalducts 9, on either side of the bore 2, which communicate with the latterat their end and into which the marginal channels of the tube 4 openout.

The ends of the slots 3 open out outside the body 1, and therefore haveto be closed off in order to ensure leaktight communication between thechannels 5 and the bore 2. To that end, the body 1 rests, by the lowerhalf of its surface, in a cradle 10 made of rolled sheet metal. Each ofthe lateral edges 11 of the cradle 10 is equipped with a series of teeth12 which fasten onto a longitudinal step feature 13 provided on thecorresponding side of the body 1.

FIGS. 1 and 3 further show a transverse partition 14 which, in the axialdirection, delimits at least one chamber 15 within the bore 2. Atransverse aperture 16 is formed at the lower part of the body 1 inorder to insert the partition 14 and is filled in by the partition inits final position. One or more transverse partitions can thus beprovided, in order to limit the internal volume of the manifold axiallyand/or to divide it into different chambers.

The cradle 10 features transversely elongate apertures 17, of a sizewhich is just sufficient for the Lubes 4 to pass through. The cradle isbrazed to the body 1, to the tubes 4 and to the partition 14, by meansof a brazing alloy applied, for example, over its entire concave uppersurface, thus ensuring leaktightness between the bore 2, the slots 3 andthe channels 5 on the one hand, and the outside on the other hand. Thepartition 14 should, moreover, be brazed to the wall of the bore 2 inorder to ensure the leaktight separation thereof.

FIGS. 1 and 3 show a tapping 19 provided at one end of the bore 2 forscrewing in a fluid inlet or outlet union.

The lower ends, not represented, of the tubes 4 may be in communicationwith a lower manifold similar to the upper manifold, as is the case inthe heat exchanger represented in FIG. 4, where elements similar tothose described previously are allocated the same reference numbersincreased by 20, and will not be described in detail again.

This second heat exchanger comprises tubes 24 similar to the previouslydescribed tubes 4, and two manifolds the bodies 21 of which differ fromthe body 1 in that each of them features not one but two longitudinalbores 22 the axes of which are parallel and situated in the samehorizontal plane, for a vertical orientation of the tubes. The two boresof each body 21 are thus separated from one another by an intermediatelongitudinal wall 38. Transverse slots 23, similar to the slots 3, areformed in the bodies. The deepest part of each slot thus defines, inaddition to two horizontal ducts 29 each of which is linked to a bore 22at the adjacent end of the slot, a horizontal duct 29a linking the twobores together, and into which open out the circulation channels 25situated in a central region of the width of the tube 24. It is alsopossible to provide for the channels 25 situated in the marginal regionsof the width of the tube to open out beyond the bores 22, that is to sayin the ducts 29, as is the case for the heat exchanger of FIGS. 1 to 3.

A cradle 30 is associated with each of the manifolds, which, in additionto its shape matched to the width of the body 21, differs from thecradle 10 described above in that the teeth 12 are replaced by rims 32projecting in the direction of the median longitudinal plane of the heatexchanger and interacting over the entire length of the cradle with acorresponding lateral step feature 33 of the body.

In FIG. 5, where elements similar to those of FIGS. 1 to 3 are allocatedthe same reference numbers increased by 40, two manifolds are againrepresented communicating respectively with the upper and lower ends ofvertical tubes 44 similar to the previously described tubes 4 andaligned, like them, alternately with spacers 46. Each manifold comprisesa solid body 41 of a generally cylindrical shape similar to that of thebody 1, and traversed like it by an axisymmetric cylindrical axial bore42. A cradle 50 made of stamped sheet metal is associated with each body41. Each end of the tubes 44 is capped by a cup 60 formed by stamping ofthe cradle, the bottom 61 of this cup fitting into a transverse notch 62of the body 41, which communicates with the bore 42 and which opens outat its ends onto the two sides of the body. An aperture 63 passingthrough the bottom 61 at its centre allows fluid communication betweenthe bore 42 and the channels 45 of the tube, the leaktightness of thiscommunication being ensured by brazing the cup by its inner face to theperiphery of the tube and by the outer face of its bottom to the notch62 of the body.

The mechanical fastening of each cradle 50 onto the corresponding body41 is achieved by means of lugs 64 belonging to the cradle, arranged inpairs on either side of the body, the pairs of lugs being arrangedalternately with the cups 60. Each lug 64 is turned away from the spacer66, that is to say upwards in the case of the upper cradle and downwardsin the case of the lower cradle, and terminates in a tooth 65 whichprotrudes in the direction of the axis of the body so as to interactwith a longitudinal step feature 53 thereof, in the same way as theteeth 12 of the heat exchanger of FIGS. 1 to 3.

A transverse partition 54 is seen in FIG. 7, which is inserted in thesame way as the partition 14 of FIGS. 1 to 3 through an aperture 56 ofthe body 41, this aperture being turned towards the tube bank, so as todelimit a chamber 55 in the bore 42. In its final position, thispartition protrudes beyond the aperture 56, so as the form the startbase for two lugs 66 which extend in the circumferential direction alongthe body 41 as far as the step features 53, onto which they are fastenedby terminal teeth 67 which act in the same way as the teeth 65.

What is claimed is:
 1. Heat exchanger for extracting heat from arefrigerant fluid in a motor-vehicle air-conditioning installation,comprising at least one manifold an internal volume of which is definedby at least one longitudinal bore (2) formed in an elongate solid body(1), and is in fluid communication with a row of tubes (4) which aremutually aligned in an axial direction of the at least one bore,elongate parallel to one another in a first direction substantiallyperpendicular to the axial direction and having an elongated crosssection in a second direction substantially perpendicular to the axialdirection and substantially perpendicular to the first direction,wherein only a part of the length of the cross section of the tubesprojects, along the first direction, into the internal volume, theleaktightness of the fluid communication between the tubes and theinternal volume being obtained by means of a cradle (10) in the form ofa profiled strip, accommodating said body and brazed to it and to theperiphery of the tubes, and wherein one end of each tube is engaged in aslot (3) formed in said body, elongate in the second direction, openingout at its two ends and the bottom of which is interrupted by theinternal volume, said cradle being applied to the body in such a way asto cover over the slots and exhibiting, opposite them, elongateapertures (17) for the leaktight passage of the tubes.
 2. Heat exchangeraccording to claim 1, in which at least one end of the length of thecross section of the tubes (4; 24) projects, along said first direction,beyond the at least one bore (2, 22) in the second direction.
 3. Heatexchanger according to claim 1, in which an intermediate part of thelength of the cross section of the tubes projects, along said firstdirection, between two bores (22) defining said internal volume.
 4. Heatexchanger according to claim 1, in which each slot features two lateralregions of a reduced depth the bottom (7) of which serves as an abutmentfor the end of the tube and a deeper central region defining a freespace (9) which communicates with the inside of the tube.
 5. Heatexchanger according to claim 1, in which the body and the cradle featuremeans (12, 13) for mutual mechanical fastening.
 6. Heat exchangeraccording to claim 5, in which said fastening means comprise two stepfeatures (13) extending in the axial direction on the outer surface ofthe body, respectively on either side of a plane passing through theaxes of the tubes, and interacting with teeth (12) of the cradle. 7.Heat exchanger according to claim 1, in which the manifold (1) includesat least one transverse partition (14) delimiting, in the axialdirection, at least one chamber (15) which forms part of said internalvolume, engaged in an aperture (16) of the body which is covered over bythe cradle (10).
 8. Heat exchanger according to claim 1, wherein theelongated cross section defining a width of the tubes is greater thanthe diameter of the at least one bore.